Process of treating coated metals.



WITED STATES PATENT OFFICE.

BRADLEY DEWEY, OF PITTSBURGH,

PENNSYLVANIA, ASSIGNOR TO AMERICAN SHEET & TIN PLATE COMPANY, OFPITTSBURGH, PENNSYLVANIA, A CORPORATION OF NEW JERSEY.

PROCESS OF TREATING COATED METALS.

No Drawing.

To all whom it may concern:

Be it known that I, BRADLEY DEWEY, a citizen of the United States, andresident of Pittsburgh, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Process of Treating CoatedMetals, of which the following is a specification.

My invention relates to a process of treating metal coated metallicmaterials having an iron base, such as sheets and plates, pipes, tubes,nails, wire, and the like, and, while not restricted to such use, moreparticularly relates to a process of treating such materials afterhaving been galvanized or coated with spelter.

The object of this invention is to provide a novel process of treatingmaterials coated with another metal or a loy of metals by galvanizing orby any other method, whereby the materials are tight coated or coated insuch manner as will permit the coated materials to be formed intoshingles, metal window frames and other articles after such treatment,without causing the coating to flake off when subjected to the severebending and pressing operations involved in making such articles.

The only method of commercially at coated materials relies upon itsability to produce the desired tight coating upon the application of anextremely small amount of spelter. This method, While making tightcoated materials, makes a product which usually hasinherentdisadvantages due to the presence of an abnormally large amountof lead in the galvanizing pot.

By treating galvanized materials, or materials coated in other ways, inaccordance with my improved process, it is made possible to producecoated materials, having a bright, clean and relatively heavy coating ofspelter or other metal or alloy of metals, but fully as tight or firmlyadherent as the best quality of product-s heretofore made, having a muchthinner or lighter Weight of coatingl.

As is well known, three distinct and well defined layers, comprising thesteel base and the pure zinc outer layer of coating which are joinedtogether by a layer composed of zinc iron alloys.

galvanizing practised Specification of Letters Patent.

present for making tight galvanized sheets have Patented Mar. 18, 1919.

Application filed December 12, 1912. Serial No. 736,302.

Under ordinary conditions the outer layer of zinc is tightly adherent tothe zinc iron alloys forming the intermediate layer, but the layer ofzinc iron alloys will readily separate from the steel base whensubjected to severe bending such as being doubled upon itself, thisintermediate stratum or layer of iron zinc alloys being hard and brittleand but weakly bound to the steel base forming the inner layer.

I have discovered that by heating galvanized or metal coated materialsto a temperature ranging from about 410 to about 600 degrees Fahrenheit,and preferably between 420 and 575 degrees Fahrenheit and maintainingthe heated materials at a temperature Within such range for a definitelength of time, which time varies, depending upon the temperature towhich the materials are heated and the rapidity with which suchtemperature is reached, that instead of being easily separated, thelayer of zinc iron alloys and the steel or other metal base become verytightl bound one to the other.

This tightening action is believed to be due to the iron and zinc at thejunction of the alloys layer and the basev gradually passing into solidsolution in one another to a greater or lesser extent, in this wayknitting the two layers together in such manner that a slight Verticalfracture through the coating no longer results in large flakes of thecoating peeling off the materials, but at most shows an almostimperceptible roughness.

I have discovered also that when maintained for too long a time bet-weenthe range of temperatures given, 4:10 to 600 degrees, the zinc or outerlayer of the coating is caused to deteriorate and will then peel andflake off.

My invention consists in heating coated materials 3T0 a temperaturehaving, in the case of spelter coated materials, an extreme range of 410to 600 degrees, more desirably between 420 and 575 degrees, andpreferably between 450 and 560 degrees Fahrenheit, and maintaining thematerials between the high and low points in such ranges in temperaturefor a time interval varying inversely with the temperature at which theheated materials are held and of from ten minutes to as much as sixhours in extent.

In carrying out the steps of my improved after being metal or alloy ofmetals in any known man ner, is placedwi'thin a muflie furnace and thetemperature'of the materials is raised bythe application of heat. Thetemperature of the furnace is then regulated to heat the coatedmaterials at a temperature of between 410 and 600 degrees Fahrenheit.

When materials are treated in accordance with my improved processimmediately galvanized or coated it maybe found that the temperature ofthe materials when placed in the treating furnace will be higher thandesired. In such cases, the temperature of th furnace will be regulatedto reduce the temperature of the materials to that desired.

More desirably this range in temperature is restricted to between 420and 57 5- degrees Fahrenheit, as the time interval in which thematerials are maintained at a definite temperature with such rangesvaries inversely with the temperature to which the materlals are heated.

With some classes of materials the range in temperature is preferablylimited to the still narrower range of between 4:50 and 560 degreesFahrenheit, but it is to be understood that my improved process may becar-- ried out when thecoated'materials are heated to atemperature-withn 410 and 600 degrees Fahrenheit and are maintainedWithin such range in temperatures for a time interval and are thenallowed to cool.

In all cases care will be taken to heat the materials being treateduniformly.

The advantages of my improved process arise from the resultingtightening of the spelter coating or other coating material upon thematerial forming the base so as to obtain a metallic coating which is astightly adherent as the best coated materials made .by the processesheretofore known, and in this way producing coated materials which arebright and clean and on which a heavy coating of any desired thicknessor weight is obtainable.

The construction and arrangement of the furnace employed in carrying outmy improved process may be modified in many ways. Means may be employedto create an air current or currents within the chamber of a mufilefurnace in order to uniformly heat all portions of the materials placedwithin the furnace. The heating step may be found to be applicabledirectly instead of by conduction as in a muffle furnace, and otherchangesmay be made without departing from my invention as defined in theappended claims. I claim 1. The process of treating galvanized materialsto tight coat the same, which consists in heating the coated materialsto a temperature ranging from 410 to 600 degrees Fahrenheit, maintainingthe materials at a temperature within said range for a time interval offrom ten minutes to six hours, thecool.

3. The process of treating metal coated materials having an iron basewhich consists in heating the coated'materials to a temperature rangingfrom 450 to 560 degrees Fahrenheit, maintaining the materials at atemperature within such range for a time interval of from ten minutes tosix hours, the time interval varying inversely with the temperature atwhich the materials are maintained, and then permitting the materials tocool.

4. The process of treating materials having an iron base coated withzinc to tight coat the same which consists in heating coated materialstoa temperature of at least 410'degrees Fahrenheit, holding the materialsat such temperature for a t1me interval my hand. BRADLEY DEWEY.

and then permitting Witnesses:

CARL L. SCHUMANN, FRANK B. Comm.

